This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The early hormone environment has been thought to influence the development of male/female behavioral and neuroendocrine differences through the life span. This study exposed developing male and female rhesus monkeys to atypical prenatal hormonal environments and has been investigating their behavioral and neuroendocrine development. Treatments were designed to mimic accidental exposure to or suppression of androgens prenatally. This study investigated whether prenatal androgen exposure, social rank, and body weight are factors regulating pubertal development in female rhesus monkeys. Subjects'mothers received injections of testosterone enanthate (20 mg/week), flutamide (an androgen receptor blocker, 30 mg/kg twice daily), or vehicle during gestational days 35/40-70 (early) or days 105/110-140 (late). We investigated whether reducing endogenous T prenatally affected adult copulatory behavior in male rhesus monkeys. Treatment with flutamide early in gestation resulted in males with significantly less masculinized genitals that control males or males getting flutamide late in gestation. During the current year all of the prenatally treated males and females along with concurrent controls were MRI scanned to look for sex differences in brain anatomy. In collaboration with investigators at the National Institute of Aging control MRI scans of males and females are being evaluated for structural sex differences. The prenatally treated animals are then being compared to the common morphed brains of control males and females to identify where prenatal treatments have modified brain structures.